CAN'T FIND NEUTRAL WHEN HOT

[StevieWonder]

Hi All,

It is usually very difficult if not impossible to select neutral on my 1970 CB750 K0 when hot or properly up to temperature. No problem when cold or warming up. Clutch seems fine, correct play before de-engaging, no drag when fully depressed. Could this be a selector problem or am I looking at a gearbox overhaul?

All advice appreciated.

[Nurse Julie]

Sounds like a cable adjustment problem more than anything else. Some of my SOHC/4' are a bit tight to get into neutral when hot but obviously not impossible, but I consider this normal on these old bikes, metals expand when they're hot so things do get tight.
Edit.. Should also have asked if you're trying to get into neutral when stationary when the engine is hot? That can be almost an impossibility at times, just rock the bike backwards and forwards and it should find neutral with no problem if everything is in order.

[Spitfire]

Yes Julie is right about that, trying to get into neutral on mine when stationary is a trial so I normally snick it into neutral before stopping, or when stopped cut the engine and put it in then.

Cheers

Dennis

[StevieWonder]

Thanks both. I have tried rocking the bike when stopped, but it rarely helps. I'll try snicking it in when coming to a stop, but would like it to be able to select it when stopped. Was never this bad on previous bikes.

[Nurse Julie]

I may be thinking of someone else but if I remember correctly, your bike has only done a few thousand miles in the whole of its life, therefore it would be almost impossible for parts to wear out, go beyond spec, break etc in such a few miles, unless someone in its past life had a bad habit of stamping or standing on the gear change lever with all their weighet and causing internal damage. I would still be looking at cable adjustment at this stage personally.

[K2-K6]

Are you completely confident the clutch isn't slipping,  at all?
 If it does,  then it'll heat the clutch pack and prevent you fully opening the clutch when hot.

If it works when cold,  it suggests the mechanical components of the gearbox are OK and wouldn't need looking at.

Most of these are very concise regarding clutch operation setup, can you post a picture of the engine end of clutch cable looking straight onto it? To see if we can spot anything.

[StevieWonder]

Yes Julie, only completed some 750 miles since top end overhaul, but no idea what the total mileage is or if the clutch has ever been changed.

K2-K6, Haven't ever notice any clutch slip, not as smooth as it might be and range from first bite to fully engaged could be wider. Am yet to give it a handful of throttle or pass 5,000 revs. Attached photo shows clutch level, with handle bar lever untouched. Would have liked to see it more in a 7 o'clock position.

All comments appreciated.

Steve

[K2-K6]

To me the lever is too far rotated anti-clockwise.

To set it,  remove cable from arm,  undo locknut,  and then adjust screw until you can just feel it has no movement on the arm.  This tells you that you've taken all of the clearance out of the clutch thrust mechanism.  Now back the screw out slightly until you get 2 to 3 degrees of arm movement,  this demonstrates you've now got running clearance.

Only now fit and adjust the clutch cable.  The cable should have enough slack (just) in it to avoid you loosing the rotating play in the arm,  with the spring able to hold the play in clockwise direction.

Then try it like that 

[StevieWonder]

Thanks K2-K6, I have quite recently set the clutch in a similar manner to how you described, by using the procedure in the Owners Manual. I will do again using your description and in the hope that I can get it closer to 7 o'clock.

Gave it a run out today, before any adjustment, only about 10-miles, with air temp much cooler than I usually ride it. Interestingly, selecting neutral was noticeably easier.

Will update when I had a chance to make adjustments as you describe.

Regards
Steve

[Nurse Julie]

Thanks K2-K6, I have quite recently set the clutch in a similar manner to how you described, by using the procedure in the Owners Manual. I will do again using your description and in the hope that I can get it closer to 7 o'clock.

Gave it a run out today, before any adjustment, only about 10-miles, with air temp much cooler than I usually ride it. Interestingly, selecting neutral was noticeably easier.

Will update when I had a chance to make adjustments as you describe.

Regards
Steve

Just a thought Stevie Wonder.... If I remember correctly the handbook has an error in it in relation to the setting up. I think it says words along the lines of 'turn it in until it touches and then turn ½ a turn clockwise' or words to that effect. It should read 'turn it in until it touches and turn ANTI CLOCKWISE ½ a turn'. You may well have sussed this yourself but I thought I would mention it just in case.

[gp_st3]

Difficulty finding neutral when stationary with a fully hot engine has been a problem for me most of the eight years I've had my K2. Basically, everything works perfectly when engine is cold / warming up but becomes next to impossible when the oil temp is above about 60C.
Type and age of oil makes a difference but the biggest improvement came after trying various options and finally changing to smooth rather than dimpled steels.
Current setup uses only five rather than seven square cut friction plates with stronger springs to reduce the tendency for slip when accelerating hard.
Finding neutral can still be a little hit and miss in hot weather but at least doesn't require so much effort it feels something might break!
We're not the only ones btw, there are several threads about this problem on the US forum with no real consensus on the cause(s)...

[StevieWonder]

Many thanks to all for helping me move this forward.  I have re-adjusted the clutch (yes Julie, the Owner's Manual has a small error! See later.) with the help of description from K2-K6, the lever is now in a more like 7 o'clock position and cable slack almost completely taken out. Thought we'd fixed it, as on the centre stand when hot, gears and neutral selected easily, but noted rear wheel still turning when in-gear with clutch disengaged (clutch lever pulled), which could be stopped with a boot. However when off the stand, couldn't get neutral 

gp_st3 has described my very similar issue perfectly. Has clearly gone to some lengths with fewer and non-dimpled steel plates. Be grateful for a lead to the source of these. CMS site picture looks smooth. DSS doesn't have picture but can order them in.

So for what it's worth, the way I see it: There is a clutch issue, not a slip problem but drag or not fully disengaging. This puts torque into the gearbox, not enough to drive the bike forward, but places cogs under tension, resulting in difficulty pulling them apart and finding neutral.

With a wet (running in oil) clutch one might expect more drag when cold (I use mineral oil - synthetic should be smoother?). So I need to inspect the clutch, maybe some of the clutch plates are buckled or perhaps the lifting mechanism has inadequate range and can be improved? Whilst it's out might as well do a full service and include friction plates and springs.

Owner's Manual Page 58. "Loosen the clutch lifter adjusting screw lock nut '2', turn the clutch adjusting screw in the counterclockwise direction 'B' (correct so far) until a slight resistance is felt (wrong: until it loosens). From this position, turn the adjusting screw in the clockwise direction 'A' 1/4~1/2 turn. Tighten the lock nut '2'." Correct.

What fun!

[shifter]

Try a different make of oil next time see if that improves as I had the same problem when using Motul 5000. In one of my bikes ,

[bobv7]

I was quite surprised to read that so many SOHC owners are using 20w50 motor oil. I can't remember this weight being recommended for any Honda motorcycle since the introduction of 10w40 grades at the start of the 70's. In fact all the workshop manuals I have covering singles, twins and fours name Castrol GTX (at the time a 10w40 weight) as the prefered oil. Duckhams 20w50, also one of Castrol group brands doesn't get a mention as an option anywhere I have seen. I accept others may have a different opinion but I have never used 20w50 oil in any Honda engine; and there you are for what it's worth.

[Bryanj]

Its in the owners manual for warmer conditions